Alkaline Peptone Water an Enrichment Medium for Vibrio Species

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alkaline peptone water MLTGEEKS

Alkaline Peptone Water is an enrichment liquid medium which is recommended for the enrichment  of clinical materials containing small numbers of Vibrio species prior to plating onto a selective medium, such as TCBS Agar.It is a modification of peptone water with an  adjusted of pH 8.4.This alkaline pH of the medium allows the growth of Vibrio species while inhibiting the growth of commensal intestinal bacteria.

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Principle of Alkaline Peptone Water

  • Sodium chloride facilitates the growth of Vibrio species and maintains osmotic equilibrium.
  • The alkalinity of this medium inhibits many commensal intestinal bacteria.
  • Peptone provides nitrogen and carbon source, long chain amino acids, vitamins and other essential nutrients that enriches growth

Composition of the Medium

IngredientsGrams / Litres
Peptone10.000 g
Sodium chloride 10.000 g
Distilled water1000.0 ml
Final pH at  temperature 25°C8.4±0.2

How to Prepare Alkaline Peptone Water

  • Start by suspending 20.0 grams in 1000 ml distilled water.
  • Then heat if necessary in order to completely dissolve the medium
  • Now dispense in tubes and sterilize the medium by autoclaving at 15 lbs pressure (121°C) for 15 minutes.

Appearance of Medium after preparation

It appears light yellow coloured clear solution without any precipitate

Uninoculated Alkaline Peptone Water
Uninoculated media

Type of Inoculums

  • Faeces
  • Food samples
  • Water samples

Procedure for Inoculation

  • Inoculate the suspected specimen as soon as possible after it is received in the laboratory
  • Pick the specimen using a swab or loop and Immerse the swab in Alkaline Peptone Water
  • Incubate aerobically at  temperature between 33-37°C for 6-8 hours.
  • Now subculture  on a selective growth media for vibrio species like TCBS Agar
  • Incubate subculture plate aerobically at temperature 33-37°C.
  • Examine plate from subculture for typical colony morphology.
Also read  Laboratory Diagnostic of Hymenolepis nana (Dwarf tapeworm)

Cultural Response on Alkaline peptone water

This cultural characteristics are observed after an incubation at 35-37°C for 18-24 hours aerobically

Vibrio cholerae luxuriant
Vibrio parahaemolyticusluxuriant

For Cultural Response on TCBS Agar please refer to Thiosulfate Citrate Bile Sucrose Agar ideal for vibrio species


  • Shread, P., T.J. Donovan, and J.V. Lee. 1981. Soc. Gen. Microbiol. Q. 8:184.
  • Cruickshank, R. 1968. Medical Microbiology. 11th ed. Livingstone LTD, London, UK.
  • Lesmana, M., E. Richie, D. Subekti, C. Simanjuntak, and S.E. Walz. 1997. J. Clin. Microbiol. 35:1856-1858.
  • MacFaddin, J.F. 1985. Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria. Vol. 1. Williams & Wilkins, Baltimore, MD
  • Thiosulfate Citrate Bile Sucrose Agar ideal for vibrio species

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About the Author: Arthur Westmann

DEFFE ARTHUR (AMOEBAMANN) is the founder and author of MLTGEEKS and MLTEXPO.He’s from Cameroon and is currently a Final year State Medical Laboratory Technician (MLT MA). Beyond lab works, he’s a passionate internet user with a keen interest in web design and blogging. Furthermore He likes traveling, hanging around with friends and social networking to do in his spare time.

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